JPH06216813A - Pseudo pull-in detecting system - Google Patents

Abstract

PURPOSE:To detect a pseudo pull-in state caused by the interruption of a 2-wire circuit in a full double data communication mode. CONSTITUTION:The terminal equipments 1 and 2 are provided with the transmitter parts 12 and 22 including the scramble parts 11 and 21, the receiver parts 14 and 24 including the scramble parts 13 and 23, the hybrid circuits 15 and 25, the back ward generating parts 16 and 26, the back word detecting parts 17 and 27, the multiplexing parts 18 and 28, the multiplex separating parts 19 and 29, etc., respectively. In such constitution, both scramble generating polynomials are different from each other and the back words of both parts 16 and 26 are sampled at many points. These sampled back words are multiplexed with the transmission data and transmitted after scrambling. The received data are descrambled an the back word data undergo the multiplex separation. Then the changing points are detected by the parts 17 and 27. A normal state is decided when the number of changing points is approximates to the number of changing points of the back words. Then a pseudo pull-in state is decided when the number of changing points is approximate to the multi-point sampling frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pseudo pull-in detecting system for detecting a pseudo pull-in by a near-end echo in a data transmission system for performing full-duplex data communication by a two-wire line. The echo canceller method and the ping-pong method are known as methods for performing full-duplex data communication between terminal devices having a transmitting / receiving unit via a two-wire line. Since it is not necessary to perform time compression, there is an advantage that long-distance transmission is possible as compared with the ping-pong method. In such an echo canceller system, if the two-wire line is broken during data transmission, the near-end echo component becomes large, and this echo component may be processed as received data. It is desired to detect the condition quickly.

[0002]

2. Description of the Related Art FIG. 4 is an explanatory view of a conventional example.
0 is a terminal device, 41 and 51 are scramble units, and 42 and 5
2 is a transmitter, 43 and 53 are descramblers, and 4 and 5
Reference numeral 4 is a receiver, 45 and 55 are hybrid circuits for 2-wire to 4-wire conversion, and 60 is a 2-wire line including a data exchange network. The echo canceller provided on the 4-line side is not shown.

When the terminal device 40 is connected to the calling side and the terminal device 50 is connected to the called side via the two-wire line 60, the equalizers and echo cancellers in the receiving sections 44 and 54 are trained. Data transmission is started after this training is completed, and in the terminal device 40 on the calling side, the scramble unit 41 of the transmission unit 42 scrambles the data and the two lines are transmitted via the hybrid circuit 45. It is sent to the line 60. Called terminal device 50
In this case, the receiving section 54 is connected via the hybrid circuit 55.
Received by, and after performing waveform equalization and echo cancellation, descrambling by the descrambling unit 53,
Replay the calling party's data. Similarly, when data is transmitted from the terminal device 50 on the called side to the terminal device 40 on the calling side, the data is similarly scrambled and transmitted, and the received data is descrambled and reproduced.

In this case, the generator polynomial in the scrambler 41 of the terminal device 40 on the calling side is (1 + X ^-18 + X)
^-23 ), the descrambler 53 of the called-side terminal device 50 is set with the same generator polynomial (1 + X ^-18 + X ^-23 ) as the scrambler 41 of the called-side terminal device 40. Also, the scrambler 51 of the terminal device 50 on the called side
Is set to (1 + X ^-5 + X ^-23 ), and the descrambling unit 43 of the terminal device 40 on the calling side is
The same generator polynomial (1 + X ^-5 + X ^-23 ) as that of the scramble unit 51 of the called-side terminal device 50 is set. That is, the scrambling generator polynomial on the calling side and the scrambling generator polynomial on the called side are different from each other so that full-duplex data transmission is performed via the two-wire line 60.

The hybrid circuits 45 and 55 are configured so as to be in a balanced state including the impedance of the two-wire line 60. Therefore, during normal operation, they are sneak through the hybrid circuits 45 and 55 of the own terminal device. The level of the near-end echo component is low and the level of the far-end echo component returned from the partner terminal device is also low, and the echo canceller is retracted during training so as to be canceled by the echo canceller. Furthermore, the receiving units 44 and 54
Is descrambled by a generator polynomial different from the generator polynomial for scrambling in the transmitters 42 and 52 of the own terminal device, so only the transmission data of the partner terminal device can be reproduced by descrambling. .

[0006]

The terminal devices 40 and 50 are connected to each other via a two-wire line 60, and two terminals are connected during data transmission / reception.
If the line circuit 60 is disconnected for some reason, the hybrid circuits 45 and 55 lose their equilibrium state, so that the transmission data of the transmission units 42 and 52 are transmitted to the hybrid circuits 45 and 55.
Via the receiving unit 44, 54 of the own terminal device
Entered in. When such high level data is input to the receiving units 44 and 54, the echo canceller malfunctions, and the receiving units 44 and 54 process the high level echo component as data from the partner terminal device. It becomes a state.

Further, although the equalizer and the echo canceller are pulled in at a relatively high speed at the time of training, at the time of starting the data communication, the tracking sensitivity depending on the line state is lowered to cause temporary line deterioration. It also stabilizes it. Therefore, even when the two-wire line 60 is disconnected, the previous state is maintained for a while, and the recognition of the pseudo pull-in state is delayed. Further, since the data descrambled by the descrambling units 43 and 53 is not the transmission data of the partner terminal device, the error becomes large, so that the pseudo error can be detected by increasing the error rate. However, it takes a considerable time to detect the increase in the error rate. That is,
The pseudo pull-in due to the disconnection of the two-wire line 60 during communication could not be detected promptly. An object of the present invention is to quickly detect the above-mentioned pseudo pull-in.

[0008]

A pseudo pull-in detection system according to the present invention will be described with reference to FIG.
1, a terminal 12 having a transmitter 12 having a 1; a receiver 14 having a descrambling unit 13; and a hybrid circuit 15 that performs 2-wire to 4-wire conversion, and a scrambler 2.
1 is connected via a two-wire line 3 to the other terminal device 2 including a transmitter 22 having a number 1, a receiver 24 having a descrambling unit 23, and a hybrid circuit 25 that performs a two-line to four-line conversion. In a data transmission system for performing full-duplex data communication, the scrambling generator polynomial of the scrambler 11 of one terminal device 1 and the scramble generator polynomial of the scrambler 21 of the other terminal device 2 are different. , The backward generation units 16 and 26 and the backward detection unit 1 in the one terminal device 1 and the other terminal device 2.
7 and 27, the backwards from the backward generators 16 and 26 are multipoint sampled, the transmission data and the multiplexing units 18 and 28 are time-division multiplexed, and the scrambling units 11 and 21 scramble and transmit. , Receiver 1
Numerals 4 and 24 are descrambled by the descrambling sections 13 and 23, the multipoint demultiplexed backwards are demultiplexed by demultiplexing sections 19 and 29, and the change points are detected by the backward detection sections 17 and 27. When it is near the number of change points, it is determined to be normal, and when it is near the multipoint sampling number, it is determined to be pseudo pull-in.

[0009]

When data is transmitted through the two-wire line 3 at a speed of 9600 bps, for example, the data speed between the terminal device 1 on the one hand and the terminal device 2 on the other hand is set to 7200 bps, and the backward generation units 16 and 26 are used. To 75 bps, the backward is generated at a speed of 2400 bps by multipoint sampling, and is time-division multiplexed in the multiplexers 18 and 28. As a result, the data becomes 9600 bps, and the scrambling units 11 and 21 scramble by different generating polynomials, and the hybrid circuits 15 and 25
To the two-wire line 3 via.

When the two-wire line 3 is normal, the received data applied to the receiving units 14 and 24 via the hybrid circuits 15 and 25 are descrambled by the descrambling units 13 and 23, and the demultiplexing unit 19 and The data is separated into the data and the backward data by 29, and the backward data of 2400 bps is added to the backward detection units 17 and 27, and the change point is detected, and the number of backward change points of 75 bps is obtained. To do.

If the 2-wire line 3 is disconnected for some reason, the hybrid circuits 15 and 25 lose their equilibrium state, and the transmission data of the own terminal device is transmitted to the hybrid circuit 15 and 25.
Only the near-end echo component that wraps around via 25 becomes, and the transmission data of the own terminal device is descrambled by the descrambler 1 of the own terminal device.
3 and 23 to descramble and demultiplexer 19,
The backward data separated by 29 becomes data at a speed higher than 75 bps when the change point is detected, and the change point number is near the multipoint sampling number, so that it can be determined as pseudo pull-in.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of an embodiment of the present invention.
2 is a terminal device, 3 is a two-wire line including a data exchange network, 1
1, 21 are scramble units, 12 and 22 are transmitter units, 1
3, 23 are descrambling units, 14 and 24 are receiving units, 1
5 and 25 are hybrid circuits for performing 2-wire to 4-wire conversion, 1
Reference numerals 6 and 26 are backward generating sections, 17 and 27 are backward detecting sections, 18 and 28 are multiplexing sections, and 19 and 29 are demultiplexing sections.

When the terminal device 1 is the calling side, the generator polynomial of the scramble unit 11 is (1
+ X ^-18 + X ^-23 ), and the descrambling unit 13
The generator polynomial of is set to (1 + X ^-5 + X ^-23 ).
When the terminal device 2 is the called side, the scrambling unit 21 has a generator polynomial set to (1 + X ⁻⁵ + X ⁻²³ ), and the descrambling unit 23 has a generator polynomial (1 + X ⁻¹⁸ + X).
^-23 ) is set. If the data transmission rate through the two-wire line 3 is 9600 bps, the backward generator 1
A backward BW having a speed of 75 bps of continuous RZ code of "1" or alternating NRZ code of "1" and "0" is generated from Nos. 6 and 26 and added to the multiplexing units 18 and 28.

The multiplexing units 18 and 28 are capable of performing backward sampling of backward BW of 75 bps at 2400 bps by multipoint sampling.
Backward data BWD of 7600 bps data SD1 and SD2 are time-division multiplexed to obtain 9600 bp.
The data of s is added to the scramble units 11 and 21.
The scramble units 11 and 21 scramble by the above-described generator polynomial, modulate according to a predetermined modulation method, and send out to the two-wire line 3 through the hybrid circuits 15 and 25.

From this 2-wire circuit 3 to the hybrid circuit 1
960 applied to receivers 14, 24 via 5, 25
The data of 0 bps is subjected to waveform equalization and echo cancellation and added to the descramble units 13 and 23. The descrambling units 13 and 23 perform descrambling according to the above-described generator polynomial, and the demultiplexing units 19 and 29
7200 bps data RD2, RD1 and 2400 b
Separated from the backward data BWD of ps, the backward data BWD is added to the backward detection units 17 and 27.

The backward detection units 17 and 27 have 240
A change point of 0 bps backward data BWD from "1" to "0" and from "0" to "1" is detected. In the case of normal backward data BWD, by detecting and counting the changing points, the same changing points as the backward changing points of 75 bps can be obtained. Therefore,
In this case, it is determined to be normal. In consideration of transmission errors and the like, an allowable value of ± several% is set with respect to the reference value of the number of change points.

If the two-wire line 3 is disconnected for some reason, the transmission data via the hybrid circuits 15 and 25 will be added to the receiving units 14 and 24 as described above, and the descrambling units 13 and 23 will be described. 2400b de-scrambled by and demultiplexed by demultiplexing units 19 and 29
When the changing point of the backward data BWD of ps is detected by the backward detecting units 17 and 27, the backward data BWD is not descrambled correctly, so that the count content of the changing point shows the data of 2400 bps. That is, since the count content is in the vicinity of the multipoint sampling number, it is determined to be pseudo pull-in.

FIG. 2 is an explanatory diagram of multiplexing backward data according to the embodiment of the present invention, in which (a) is a backward BW of 75 bps from the backward generators 16 and 26,
(B) is backward data B1, B2, ... Of 2400 bps by multipoint sampling, (c) is 7200
Bps data U1, U2, U3, ..., (d) represent multiplexed data.

75 from the backward generators 16, 26
The backward BW of bps is converted into backward data B1, B2, ... Of 2400 bps by multipoint sampling in the multiplexers 18, 28, and is multiplexed with the data U1, U2, U3 ,. . In that case, since the speed ratio is 3: 1, as shown in (d),
Backward data B for data U1, U2, U3
1 is multiplexed, the backward data B2 is multiplexed with the data U4, U5, U6, and becomes 9600 bps data, which is scrambled by the scrambling units 11 and 21 and transmitted.

FIG. 3 is a block diagram of the essential parts of the backward detection unit according to the embodiment of the present invention. 30 is a demultiplexing unit, 31 is a change point detection unit, 32 is a selector, 33 is a counter 33-
A counter unit composed of 1 to 33-16, 34 an adder, and 3
Reference numeral 5 is a determination unit, and 36 is a timing control unit. Data of 9600 bps descrambled by the descrambling units 13 and 23 of the receiving units 14 and 24 shown in FIG. 1 are separated by the demultiplexing units 19 and 29 into 7200 bps data and 2400 bps backward data. The demultiplexing units 19 and 29 correspond to the demultiplexing unit 30 in FIG.

The change point detection unit 31 detects the change points of backward data from "1" to "0" and "0" to "1". The selector 32 includes counters 33-1 to 33-1.
6, for example, is sequentially switched every 1 second by a control signal from the timing control section 36, and the counter section 33 counts change points for 16 seconds. In addition, the adder 34 includes the counters 33-1 to 33-of the counter unit 33.
The count contents of 16 are added. The addition timing of the adder 34 is set every time the counters 33-1 to 33-16 are switched by the timing control unit 36.

Therefore, in a normal state, the count content of the change point of one counter indicates the number of change points of the backward of 75 bps, and the addition output of the adder 34 is 16 times that. Therefore, for example, the determination unit 35 can compare the addition output of the adder 34 with 1200, and can determine that the value is normal when the value is near 1200. Also, during pseudo pull-in, a backward rate of 75 bps cannot be reproduced due to descrambling, so the number of change points is close to 2400.
When allowing the instantaneous interruption for 1 to 2 seconds, the determination unit 35 can determine that the pseudo pull-in is performed when the addition output of the adder 34 exceeds 5850.

Further, in the above-mentioned embodiment, since 16 counters 33-1 to 33-16 are provided, the changing point of the backward data descrambled for 16 seconds is monitored. Even in the case of a line state in which disconnection is performed a plurality of times, it is possible to determine that the line is a pseudo pull-in and detect an abnormal state of the line. Of course, it is also possible to determine whether or not there is a pseudo pull-in by counting the number of change points for one second using one counter. In addition, the case where the backward is multi-point sampled so as to become the backward data of 2400 bps is shown, but the backward speed and the multi-point sampling speed can be set to those other than those in the above-described embodiment, and transmitted. The data rate can also be arbitrarily selected according to the configuration of the two-wire line and the terminal devices 1 and 2.

[0024]

As described above, the present invention is a system for performing full-duplex data communication via the two-wire line 3 by making the scrambling generator polynomials of the terminal devices 1 and 2 different from each other. In this case, the backward generators 16 and 26 and the backward detectors 17 and 27 are provided, and the backwards from the backward generators 16 and 26 are sampled at multiple points, time-division multiplexed with the transmission data, and the scrambler. 1
1 and 21 scramble with different generator polynomials, and on the receiving side, after descrambling, the change point of the demultiplexed backward data is detected by the backward detection unit 1.
7 and 27, it is judged to be normal when the number of change points corresponds to the number of change points of the backward, and when the number of change points corresponds to the multipoint sampling number, the data received by the own terminal device is included in the transmission data of the own terminal device. It is determined that the parts 14 and 24 are drawn in by a pseudo drawing, and by adding a slight configuration,
There is an advantage that the pseudo pull-in can be detected quickly.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of multiplexing backward data according to the embodiment of this invention.

FIG. 3 is a block diagram of essential parts of a backward detection unit according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram of a conventional example.

[Explanation of symbols]

 1, 2 Terminal device 3 2-wire line 11, 21 Scrambler 12, 22 Transmitter 13, 23 Descrambler 14, 24 Receiver 15, 25 Hybrid circuit 16, 26 Backward generator 17, 27 Backward detector 18 , 28 Multiplexing unit 19, 29 Demultiplexing unit

Claims (1)

[Claims] 1. A transmission section (12) having a scramble section (11), a reception section (14) having a descramble section (13), and a hybrid circuit (1) for performing 2-wire to 4-wire conversion.
5), one terminal device (1), a transmission unit (22) having a scramble unit (21), a reception unit (24) having a descrambling unit (23), and 2-wire to 4-wire conversion. The other terminal device (2) provided with the hybrid circuit (25) for performing is connected via the two-wire line (3), and scramble generation for the scramble section (11) of the one terminal device (1) is performed. In a data transmission system for performing full-duplex data communication, the polynomial and the scrambling generator polynomial of the scramble section (21) of the other terminal device (2) are made different, and the one terminal device (1) And the other terminal device (2)
Backward generators (16) and (26)
And the backward detection units (17) and (27) are provided, and the transmission units (12) and (22) of the one terminal device (1) and the other terminal device (2) generate the backward signal. The backward signals from the sections (16) and (26) are sampled at multiple points, time-division multiplexed with the transmission data, scrambled by the scrambling sections (11) and (21), and transmitted, and the receiving sections (14), (24) descrambles the received data by the descrambling units (13) and (23), separates the multi-point sampled and multiplexed backwards, and the backward detection units (17) and ( 27) The change point is detected according to 27), and it is determined to be normal when the number of change points is less than or equal to the number of change points of the backward, and pseudo pull-in is determined when the number of multi-point sampling numbers is near. Inclusion detection method.